Sorry for the very basic question: I just started commuting to work. My office building has vertical bike storage racks with hooks. I have never used vertical racks before. Some of the commuters place their front wheels on the top hook, while others hook the their frames. What is the proper way to store bikes on vertical racks? I am concerned that hooking my wheel might do damage to the brakes or gears, but I just don't know enough about bike mechanics to make an informed decision.